Noise Resistant Phase Imaging with Intensity Correlation

TL;DR

This paper introduces a phase imaging method that uses intensity correlation to achieve noise resistance against phase fluctuations, allowing for accurate low-light measurements over extended periods.

Contribution

The novel technique measures intensity correlation instead of intensity, enabling high-precision phase imaging despite phase fluctuations and low photon flux.

Findings

Achieves optimal phase reconstruction precision with two photons per phase stability time.

Demonstrates immunity to position-independent, time-dependent phase fluctuations.

Enables long measurement times in low-light conditions.

Abstract

Interferometric methods, renowned for their reliability and precision, play a vital role in phase imaging. Interferometry typically requires high coherence and stability between the measured and the reference beam. The presence of rapid phase fluctuations averages out the interferogram, erasing the spatial phase information. This difficulty can be circumvented by shortening the measurement time. However, shortening the measurement time results in smaller photon counting rates precluding its applicability to low-intensity phase imaging. We introduce and experimentally demonstrate a phase imaging technique that is immune to position-independent, time-dependent phase fluctuation. We accomplish this by measuring intensity correlation instead of intensity. Our method enables using long measurement times and is therefore advantageous when the photon flux is very low. We use a Fisher information-based approach to show that the precision of phase reconstruction achieved using our method is in fact the best achievable precision in the scenario when two photons are detected per phase stability time.